Objective: To develop a systematic and centralized approach towards our understanding of the impact of acute viral respiratory diseases on selective populations. Specifically, the Acute Viral Respiratory Diseases Unit would: 1. Evaluate the etiology of acute viral respiratory infections in selective populations (eg. infants, asthmatics, elderly, and those with other chronic pulmonary diseases). 2. Assess the pathophysiologic impact of the various respiratory viruses in the above selective populations. 3. Develop improved, rapid diagnostic techniques for viral respiratory infections. 4. Identify and or expand our knowledge on the correlates of immunity associated with protection against disease. 5. Perform clinical trials with promising new vaccines or therapies.